Lamp ballast circuit for dual voltage supplies



Sept. 29, 1970 D, L. WOOD ,5 ,5

LAMP BALLAST cmcuuron DUAL VOLTAGE 'SUPPLIES Filed April 3, 1968 I I PRIVMVHRY ,ISECONDRRY V fi /.1 5 w PRIMQRX I JJS ECONDHRY Z40 VAC- par/0% h 000f flin /275 United States Patent 3,531,686 LAMP BALLAST CIRCUIT FOR DUAL VOLTAGE SUPPLIES David L. Wood, Hendersonville, N.C., assignor to General Electric Company, a corporation of New York Filed Apr. 3, 1968, Ser. No. 718,443 Int. Cl. G05t' 1/24; H05b 41/323 US. Cl. 315280 7 Claims ABSTRACT OF THE DISCLOSURE Ballast device for starting and operating gaseous discharge lamp for use with either 120 or 240 volt alternating current supply comprises a primary winding and a secondary winding arranged in spaced relation on a closed magnetic core having a magnetic shunt between the windings, the windings being selectively connectible (1) in voltage bucking relation for connection to the 240 volt supply and (2) in voltage additive, autotransformer relation for connection to the 120 volt supply.

The present invention relates to electrical ballast devices and more particularly to such devices adapted for starting and operating gaseous discharge lamps from conventional alternating current supply sources.

It is an object of the invention to provide an electrical ballast device of the above type which is readily adapted for operation from either a 120 volt or 240 volt alternating current supply source.

It is a particular object of the invention to provide a ballast device of the above type which is simple and inexpensive in construction, which employs conventional components, and which may be made smaller in size and at less cost than known ballast devices used for the same purpose.

It is still another object of the invention to provide a method of electrically interconnecting the components of a ballast transformer of the above type for readily converting it for operation from either a 120 volt or a 240 volt supply.

Other objects and advantages will become apparent from the following description and appended claims.

With the above objects in view, the present invention in one of its aspects relates to a starting and operating circuit for a gaseous discharge device comprising a transformer having a core providing a closed magnetic circuit, a primary and secondary winding arranged in spaced relation on the core, means providing leakage re actance between the windings, the secondary winding being electrically connected with the gaseous discharge device, and means for selectively connecting the primary and secondary windings (1) in voltage bucking relation to a 240 volt alternating current supply source and (2) in voltage additive autotransformer relation to a 120 volt alternating current supply source.

The invention will be better understood from the following description taken in conjunction with the accom panying drawing, in which:

FIG. 1 is a somewhat schematic view of a ballast transformer having a structure which may be used in practicing the invention;

FIG. 2 is a circuit diagram showing the ballast components connected for operation from a 120 volt supply; and

FIG. 3 is a circuit diagram showing the components of the FIG. 2 device connected for operation from a 240 volt supply.

Referring now to the drawing, and particularly to FIG. 1, there is shown a ballast transformer 1 comprising a closed magnetic core 2, such as magnetic iron, and a magnetic shunt 3, such as a stack of magnetic iron laminations, connecting opposite legs of core 2 across the central opening of the core. Wound on a leg of core 2 are primary coil 4 and secondary coil 5 arranged spaced from each other on opposite sides of magnetic shunt 3. As shown, the turns of the respective coils are wound in the same direction on the core leg.

FIG. 2 is a circuit diagram showing the arrangement of the ballast transformer components for connecting a discharge device 6, typically a mercury vapor lamp, to a power source of volts A.C. In the embodiment shown, primary coil 4 is connected at its outer end to terminal 11, from which a connection is made to supply termianl 10 by switch 14. The inner end of primary coil 4 is connected via terminals 13 and 12 and switch 15 to the adjacent (inner) end of secondary coil 5. Terminal 13 also serves as the other terminal of the 120 volt supply source. Lamp 6 is connected between supply terminal 10 and the outer end of secondary coil 5.

In this arrangement, the primary winding 4 and secondary winding 5 are connected as a high reactance autotransformer, being loosely coupled inductively by magnetic shunt 3, and in this form the windings are in voltage additive relation. With coil 4 connected across the supply source terminals 10, 13 as shown, it constitutes the primary of a voltage step-up autotransformer, of which coils 4 and 5 constitute the secondary. Lamp 6 typically has a starting voltage of near 240 volts and the high reactance autotransformer arrangement of the windings in the FIG. 2 circuit serves to step up the 120 volts of the supply to a level sufficiently high (e.g., 240 volts) to start the lamp. As will be understood by those skilled in the art, shunt 3 provides a high leakage reactance serving to drop the starting voltage to a lower level for normal operation of the lamp after it has been started. The transformer thus acts to limit the current flow in the load circuit as is necessary due to the negative resistance characteristic of the lamp.

While the circuit of FIG. 2 is satisfactory for operation from a 120 volt supply source, it is not suitable for operation from a 240 volt source because under the latter conditions the autotransformer action of the coil windings results in an excessively high voltage being applied to the lamp. It is therefore necessary to change the FIG. 2 circuit to an arrangement wherein a proper starting and operating voltage is applied to the lamp under such conditions. In accordance with the invention the circuit of FIG. 2 is readily converted to operation from a 240 volt supply source by re-arranging the connections between the circuit components as shown in FIG. 3, wherein switch 14 is disconnected from terminal 10 and turned so as to interconnect terminal 11 and terminal 12, and switch 1'5 is disconnected from terminal 112. In this arrangement, the primary and secondary windings and the lamp are in electrical series circuit across the 240 volt source, and secondary winding 5 is so connected to primary winding 4 as to be in voltage bucking relation therewith. The two windings thus act, in effect, as two choke coils having magnetic flux paths in opposition to one another. In this arrangement, the 240 volts of the supply source are sutficient to start lamp 6, and the bucking relation of the primary and secondary windings results, after the lamp starts, in forcing a sufficient amount of magnetic :fiux through shunt 3 to cause a drop in the initial voltage to the normal operating voltage of the circuit (eg about volts).

While a particular switching arrangement has been shown in the drawing, it will be understood that various means may be employed for making the desired connections between the circuit components in accordance with the invention. For example, terminals 10, 11, 12 and 13 may be mounted in the form of terminal posts on a suitable terminal board 16, shown in interrupted lines in FIGS. 2 and 3, and suitable separable conducting members or jumper could be employed instead of switches 14 and 15 for making the alternative connections between the several terminals as illustrated.

There is thus provided by the invention a novel ballast device which may be readily converted for operation with different voltage sources and which is simple and inexpensive in construction, reliable in operation, and compact in size.

While the present invention has been described with reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art without actually departing from the scope of the invention. Therefore, the appended claims are intended to cover all such equivalent variations as come within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A starting and operating circuit for a gaseous discharge device comprising a transformer having a core providing a closed magnetic circuit, a primary winding and a secondary winding arranged in spaced relation on said core, means providing leakage reactance between said windings, said secondary winding being electrically connected with the gaseous discharge device, and means for selectively and alternatively connecting said primary and secondary windings (1) in voltage bucking relation to one another for connection to a 240 volt alternating current supply source and (2) in voltage additive autotransformer relation to one another for connection to a 120 volt alternating current supply source.

2. A circuit as defined in claim 1, said leakage reactance means comprising a magnetic shunt arranged between said windings.

3. A circuit as defined in claim 2, said core having a plurality of legs defining a central opening, said magnetic shunt extending across said opening between opposite core legs.

4. A circuit as defined in claim 3, said primary and said secondary windings being arranged on the same core leg.

5. A circuit as defined in claim 1, said connecting means comprising terminals connected respectively to the opposite ends of each of said primary and said secondary windings.

6. A circuit as defined in claim 5, said connecting means further comprising switch means for selectively interconnecting said terminals.

7. A circuit as defined in claim 5, said terminals being mounted on a terminal board, said connecting means further comprising separable connectors for selectively interconnecting said terminals.

References Cited UNITED STATES PATENTS 1,235,741 8/1917 Thomas 315280 2,114,842 4/ 1938 Iman 315-280 3,371,246 2/1968 Kawauchi et al. 315262 FOREIGN PATENTS 593,517 10/ 1947 Great Britain.

JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant Examiner US. Cl. X.R. 315282; 323-- 

